This invention relates generally to improvements in bits for drilling well bores and the like. More particularly, but not by way of limitation, this invention relates to an improved seal and bearing structure for a bit that includes a helical spring, journal bearing rotatably supporting the cutter on the bit and constantly exerting a biasing force on a face seal.
In the process of drilling oil and gas wells and the like, rotary drill bits are attached to the lower end of the drill string and engage the formation to form the well bore as the bit is rotated with weight applied thereto. Manifestly, such bits are exposed to extremely hard use in very demanding environments, and yet must perform for the maximum length of time in order to be suitable for the drilling of well bores
One type of such bits is referred to generally as a sealed bearing bit. In these bits, it is the general practice to provide a lubricant reservoir that is connected to the bearing space or cavity located between the pin and the cutter member which is rotatably mounted on the pin. To prevent the loss of lubricant from such cavity and to prevent the ingress of deleterious materials into the cavity, such cavities have been provided with various forms of seals.
The space limitations imposed by the size of the well bores drilled, the cutting structure of the bit, and the physical size thereof demands that such bearings be very compact and that such sealed bearing combinations occupy a minimum amount of space consistent with providing a bearing that will last at least as long as the cutter members themselves.
U.S. Pat. No. 4,514,098 issued Apr. 30, 1985 to Rodolfo M. Ippolito illustrates the use of a helical coil spring to form the journal bearing between the pin of the bit and the bit cutter members. It will be noted that the '098 patent illustrates the use of a seal that is of a type generally referred to as a radial seal. That is, the seal therein forms a seal between the bore of the cutter member and the outer circumference of the pin on which the cutter member rotates.
It will also be noted that the spring bearing of the '098 patent is preferably pressed in a bore in the cutter members and is thus fixed against axial movement relative thereto. While this bearing has worked generally satisfactorily, in some instances, difficulty has occurred due to the tendency of the spring bearing to remain in motion due to inertial forces once it has been set in motion.
Accordingly, an object of this invention is to provide, in one aspect, a new spring bearing and seal combination that includes a face-type seal constantly urged into sealing engagement by the resiliency of the spring bearing, and in another aspect, to securely lock the spring bearing to prevent rotation of the bearing relative to the cutter member.